Motors, pumps and bearings require frequent maintenance attention in typical commercial systems and industrial plants. With conventional maintenance strategies such as exception-based and periodic-checking, faults developed in critical equipment (e.g. pumps) have to be detected by human experts through physical examination and other off-line tests (e.g., metal wear analysis) during a routine maintenance in order for corrective action to be taken. Faults that go undetected during a regular maintenance check-up may lead to catastrophic failure and un-scheduled shut-down of the plant. The probability of an un-scheduled shut-down increases as the time period between successive maintenance inspections increases. The frequency of performing maintenance, however, is limited by availability of man-power and financial resources and hence is not easily increased. Some maintenance inspections, such as impeller inspection may require stopping the process or even disassembling machinery. The lost production time may cost ten times more than the labor cost involved. There is also a possibility that the reassembled machine may fail due to an assembly error or high start up stresses for example. Finally, periodically replacing components (via routine preventive maintenance) such as bearings, seals, or impellers is costly since the service life of good components may unnecessarily be cut short.
Cavitation, blockage and impeller damage are common problems/faults encountered with pumps. Cavitation can cause accelerated wear, and mechanical damage to pump components, couplings, gear trains, and drive motors. Cavitation is the formation of vapor bubbles in the inlet flow regime or the suction zone of the pump. This condition occurs when local pressure drops to below the vapor pressure of the liquid being pumped. These vapor bubbles collapse or implode when they enter a high pressure zone (e.g. at the discharge section or a higher pressure area near the impeller) of the pump causing erosion of impeller casings as well as other pump components. If a pump runs for an extended period under cavitation conditions, permanent damage may occur to the pump structure and accelerated wear and deterioration of pump internal surfaces and seals may occur. Detection of such conditions before they become severe or prolonged can help to avoid cavitation-induced damage to the pump and facilitate extended plant up time. Such detection also can avoid accelerated pump wear and unexpected failures and further enable a well planned and cost-effective maintenance routine. Depending on the type of pump, other problems can occur such as inlet or outlet blockage, leakage of air into the system due to faulty pump seals, or the impeller or impeller parts impacting the pump casing.
Prior efforts in pump diagnostics have included vibration analysis and acoustic analysis techniques. For example, a modern chemical plant may require a service engineer to physically go to hundreds or even thousands of critical pumps periodically (e.g., monthly) to record vibration data from the pump. The data is then subsequently analyzed using vibration analysis algorithms to detect pump problems such as broken impeller vanes or out of balance conditions. Other research efforts have looked at performing pump diagnostics using process instrumentation such as flow meters and pressure transducers. Some efforts have looked at the relationship between inlet and outlet pressures and flow rate with pump speed to determine if a pump problem exists. Others have performed trending on these parameters over time.
Still other techniques have focused on signal analysis of unconditioned process sensors, such as flow sensors and pressure sensors. Flow sensors such as orifice-plate differential pressure, vortex, turbine, time-domain pressure techniques are invasive sensors and must be installed in-line within the process framework or pump system. Other flow sensors such as corriolis flow meters, are extremely costly and must be installed in-line with process piping.
In view of the above, there is a strong need in the art for a system and/or method for condition monitoring which mitigates some of the above-noted problems associated with conventional pump monitoring systems and/or methods.